The present invention relates to a radioactive source wire and a dual lumen catheter system for positioning a radioactive material in the body for brachytherapy. More particularly, the invention relates to a radioactive source wire and dual lumen catheter system for positioning a radioactive material at a desired site in the body without direct contact between the radioactive source and body tissue.
The body""s healing response to wounds includes the formation of scar tissue. This response occurs in the vascular system after injury or trauma such as may be caused by angioplasty or other similar treatments thereby resulting in a condition commonly referred to as restenosis. As a result of restenosis, scar tissue grows on the inner walls of the vessels vascular system thereby causing an undesirable narrowing of the vessels. Accordingly, it is desirable to prevent or inhibit restenosis as part of the overall treatment of the vascular system following procedures such as angioplasty or the like. While angioplasty currently has a short-term success rate of 90-95%, due to restenosis, about 30-50% of patients"" vessels narrow to approximately 50% or less of the size of the native vessel.
A variety of different therapies for the prevention of restenosis have been employed including light therapies, chemotherapeutic agents, stents, atherectomy devices and lasers. One method for preventing or inhibiting restenosis that has shown promise is the irradiation of the inner vascular wall subsequent to angioplasty in order to prevent or inhibit scar tissue formation sometimes referred to as intimal hyperplasia. However, the devices for delivery of radiation sources to the treatment site suffer from a number of drawbacks that limit their usefulness and effectiveness.
U.S. Pat. No. 5,503,614 (Liprie) relates to a flexible source wire for radiation treatment of diseases. The source wire includes a radioactive source and may be maneuvered to the site of treatment via various vessels in the body. The flexible source wire includes a flexible housing formed by an elongate, hollow tube such as Nitinol(copyright) or a titanium/nickel alloy which exhibits little or no memory retention when bent. The disclosed device also includes an internal flexible backbone wire for placement within the hollow tube and which may be constructed from the same material as the hollow tube.
U.S. Pat. No. 5,833,593 (Liprie) relates to a flexible source wire for localized internal radiation of tissue which is capable of maneuvering through tortuous narrow body vessels. The source wire is provided with an elongate, flexible housing tube having one end modified to receive a radioactive core. The source wire may be constructed from nickel/titanium alloys. Both ends of the source wire are sealed and the end containing the radioactive material is rounded to ease navigation of body vessels.
U.S. Pat. No. 5,084,002 (Liprie) relates to an ultra-thin, high dose iridium source for remote treatrrfent of cancerous tissue with radiation. This device is specifically designed for use in areas of the human body where minimization of trauma to adjacent tissue is a high priority. As a result, the radioactive source is encapsulated in a thin platinum delivery wire with an ultra-thin cross section. A similar device is also disclosed in U.S. Pat. No. 5,141,487 (Liprie).
U.S. Pat. No. 5,302,168 (Hess) relates to a method and apparatus for restenosis treatment after angioplasty by application of a radioactive dose to the reduced region of the artery. In one embodiment disclosed in this patent, a radioactive dose is positioned in a housing located at the distal end of a catheter delivery device. The housing is provided with a window cutout covered by a sheath. The sheath is drawn back when the radioactive dose is positioned for treatment. A second embodiment disclosed in this patent involves attaching radioactive elements to an angioplasty balloon catheter and expanding the balloon in the area to be treated to force the radioactive elements into contact with the area to be treated.
U.S. Pat. No. 5,213,561 (Weinstein et al.) discloses methods and devices for preventing restenosis after angioplasty. More specifically, various embodiments are disclosed wherein a radioactive source is mounted at the end of a guide wire, is delivered inside a tube provided with a guide wire in a balloon catheter or is coated on a balloon expandable stent. A retractable sheath is employed to enclose the radiation source until irradiation is desired at which point the sheath is retracted.
U.S. Pat. No. 5,199,939 (Dake) discloses a radioactive catheter and a method for using the catheter for preventing restenosis after angioplasty. The method includes employing an elongate, flexible catheter with a radioactive source located in its distal end to irradiate the treatment zone. The radioactive catheter employs a plurality of cylindrical radioactive pellets disposed among a plurality of cylindrical spacers as the radioactive source.
The foregoing catheter systems suffer from a number of drawbacks. For example, many of the devices include a number of elements located between the radiation source and the area to be treated which results in shielding which may reduce the effect of the radiation and/or cause an irregular distribution of the radiation dose. Other devices provide the radioactive source material in a plurality of discrete elements which inherently results in different levels of radiation dose being applied to different parts of the treated area. Still other devices require repeated feeding and removal of a guidewire to locate the radiation dose and remove the radiation dose thereby making the treatment awkward and time-consuming for medical personnel. Other drawbacks of specific devices exist as well.
It is an object of certain embodiments of the present invention to overcome one or more of the drawbacks of existing devices for providing a dose of radiation to a localized treatment area in the body.
It is a further object of certain embodiments of the present invention to provide an improved radioactive source suitable for navigating tortuous narrow body vessels in order to position the radioactive source in close proximity to the treatment area.
It is a further object of certain embodiments of the present invention to provide devices wherein shielding of the radiation is minimized or substantially eliminated.
It is a still further object of certain embodiments of the present invention to provide devices that deliver a substantially uniform radiation dose to the area to be treated.
It is a still further object of certain embodiments of the present invention to provide a dual lumen catheter system for delivery of a radioactive source to a treatment area without contact between the radioactive source and body tissue
These and other objects are accomplished by various embodiments of the present invention, which relates, in one aspect, to a radioactive source wire having a tapered distal end with which a radioactive material is associated. The source wire of the present invention may be made as a single unit thereby greatly reducing the chance that a portion of the source wire can break off during use. Also, the tapered distal end of the source wire allows the application of additional useful elements to the radioactive source wire while still providing a source wire having a diameter within a predetermined size range.
The present invention also relates to a dual lumen catheter system for delivery of a radioactive source wire to a localized area to be treated. The radioactive source wire may be a source wire in accordance with the present invention. The dual lumen catheter system includes structure that allows insertion of the radioactive source wire into the body without direct contact between the radioactive source wire and body tissue. Various embodiments of the dual lumen catheter system of the present invention overcome some of the drawbacks of prior art devices.